Hiya CZ 
Yeah, the M357-A1 can swap strait across with the 40SW barrel. I have had the opportunity to shoot both and the 40SW barrel has more recoil and is less accurate for me. Sounds like you like doin' the back and forth thing tho so you'll have no problems likin' the M-A1's. If ya like the P239, you'll really like the feel of the M357-A1 in your hands.
Give us a range report after you've put a few rounds through 'er.
Wulf
Yeah, the M357-A1 can swap strait across with the 40SW barrel. I have had the opportunity to shoot both and the 40SW barrel has more recoil and is less accurate for me. Sounds like you like doin' the back and forth thing tho so you'll have no problems likin' the M-A1's. If ya like the P239, you'll really like the feel of the M357-A1 in your hands.
Wulf